Linear actuators create motion in a straight line, in contrast to the circular motion of a conventional electric motor. Such actuators are designed for use where a motor drives a threaded shaft and a corresponding threaded coupled nut such that rotary motion of a control knob or handle is converted into a linear displacement via screws, gears or other similar devices. Most electro-mechanical linear actuator designs incorporate a lead screw and lead nut. Balls screws and ball nuts also may be used. In both instances the screw may be connected to a motor or manual control knob either directly or through a series of gears. Gears are typically used to allow a relatively small motor spinning at a higher rotational speed to be geared down to provide the torque necessary to spin the screw under a heavier load than the motor would otherwise be capable of driving directly.
Presently there exist at least two methods of integrating a lead nut into a motor rotor. In one method, an injection molding technique is used where a threaded lead nut is injection molded into the rotor. However, this is a permanent solution and effectively eliminates the ability to swap out nuts or rapid prototype, that is, if the lead nut is already threaded, inventory must be increased to handle all of the different lead nut/screw combinations. In addition, complicated dies must be used to properly create the lead nut threads to match the lead screw. Material shrinkage must be controlled precisely to prevent poor thread match from nut to screw.
In a second method, adhesives are used to bond the lead nut to the stainless steel rotor inner diameter. However, this method requires a precision interface, additional surface preparation, and cure time. Furthermore, this method has relatively decreased strength and torque capability. As is the case with the first method, the second method is a permanent solution where once the interface is achieved risk of system damage prevents disassembly and continued use of components.
In addition, prior art linear actuators that are constructed as described above suffer from suboptimal load capacity and screws of relatively smaller diameter.
This disclosure describes improvements over these prior art technologies.